Wrought copper-nickel alloy

ABSTRACT

WROUGHT COPPER-NICKEL ALLOYS CONTAINING SPECIAL AMOUNTS OF CHROMIUN EXHIBIT IMPROVED RESISTANCE TO THE IMPINGEMENT EROSION EFFECTS OF HIGH VELOCITY SEAWATER. SMALL AMOUNT OF IRON ALSO IMPROVE &#34;PARTING&#34; CORROSION CHARACTERISTICS OF ALLOYS OF LOWER NICKEL CONTENT.

April 17, 1973 z g 025 w Y F. A. BADIA ETAL 3,728,106

WROUGHT COPPER-NICKEL ALLOY Filed Nov. 13, 1969 Ewes/w- Aim EL INVENTORS' Ram 4277/? 590/ v BY 0M0 59PM? Glswy 0'51. hear United States Patent 3,728,106 WROUGHT COPPER-NICKEL ALLOY Frank A. Badia, Ringwood, N.J., David B. Anderson, Wilmington, N.C., and Gary N. Kirby, Ann Arbor, Mich., assignors to The International Nickel Company, Inc., New York, N.Y.

Filed Nov. 13, 1969, Ser. No. 876,541

Int. Cl. C22c 9/06 US. Cl. 75-159 7 Claims ABSTRACT OF THE DISCLOSURE Wrought copper-nickel alloys containing special amounts of chromium exhibit improved resistance to the impingement erosion efi'ects of high velocity seawater. Small amount of iron also improve parting corrosion characteristics of alloys of lower nickel content.

The subject invention is directed to various wrought, non age-hardenable copper-nickel alloys and articles fabricated therefrom capable of affording improved resistance to corrosive media, including chlorides, notably seawater.

Though the origin of copper-nickel alloys, commonly termed cupronickels, can be traced at least to the time when the Greeks (-B.C.) used an alloy containing approximately 77.5% copper and 20% nickel as a coinage material, it was not until just before the turn of the present century that such an alloy (85% copper-15% nickel) was utilized for its corrosion resistant qualities as tubing, the product form in which a most substantial percentage of the cupronickels has been and continues to be used. In retrospect, however, even this pioneer venture appears to have been of limited scope since various writings in treating the historical development of the copper-nickel alloys reflect that it was not until the advent of the 70/30 alloy (circa the early 1920s) that the cupronickels really came into prominence as materials uniquely capable of resisting the aggressiveness of salt water environments.

Conventional commercially used cupronickels in terms of their virtue to resist seawater attack have been, as is generally known, particularly effective in quiescent and low velocity seawater. In contrast, above, say, a velocity of 10 to feet per second (f.p.s.) such alloys inherently suffer from the considerably less attractive characteristic of manifesting a much greater susceptibility to undergo impingement erosion. Conducive to understanding the significance of this drawback, reference might be made to the manner in which such alloys are thought to thwart seawater attack. In common with any number of other corrosion resistant materials such as the stainless steels, the cupronickels are generally considered to owe their corrosion resistant nature to the formation of a surface protective film, a film which, at least in part, contains oxide(s) and which performs the role of a barrier to penetration by corrodents.

Now, under the usual conditions prevailing in connection with stagnant or low velocity seawater, situations in which localized corrosion (e.g., crevice and pitting), is of particular concern, it seems that the protective film is particularly difficult to penetrate or rupture. In any case, it adheres to the metal surface with such tenacity as to offer appreciable resistance to removal by normal external forces. Moreover, if the film is pierced, the environmental conditions are such that the ruptured area ostensibly undergoes self-healing, as it were, meaning the film is restored, there apparently being sufiicient oxygen available to assist in reforming or repairing the oxide film. Also in stagnant and low velocity seawater should a pit form the corrosion rate at that point is often quite slow and has been known, with time, to even cease.

However, with rapidly moving seawater, the above is 'ice not the case. High velocity seawater apparently greatly inhibits or interferes with the formation of the protective film. That is to say, the force of a high velocity salt water stream may pro se induce film rupture (at least in large measure it contributes) or should penetration otherwise occur, the very force of the velocity tends to erode the film as it is being self-restored through oxygen replenishrnent at the rupture site. Put another waythere is a continuous but competitive process of film formation and disruption simultaneously occurring.

Translating the above to actual commercial operation and using tubing (condenser, heat exchanger, etc.) for purposes of illustration, as seawater passes through tubing it commonly encounters obstructions, restrictions and the like as well as bends. These regions naturally tend to interrupt or alter the normal seawater fiow pattern and, as a consequence, create a condition of turbulence. This in turn can and too often does result in high velocities at localized areas-the very environment conducive to impingement erosion. This condition while it can be minimized by proper equipment design cannot be eliminated in all systems. Accordingly, under normal commercial operations the same system can encounter and thus must contend with the peculiarities of both low and high velocity seawater.

Though there undoubtedly have been efforts to obviate the disadvantage above discussed, the literature reflects, however, insofar as we are aware, that there apparently have been but two significant improvements in respect of the corrosion resistance of the conventional wrought, non age-hardenable cupronickels in the past 40-45 years. Briefly, one involved the incorporation of approximately 0.4% to 1% iron to the 70/ 30 composition, the other the addition of approximately 1.2% iron to the 90/10 type (the latter not being of concern herein). In neither instance is the long standing susceptibility to high velocity seawater appreciably lessened. And indispensible in minimizing resistance to impingement erosion-it must be emphasized that it can not be accomplished at the expense of crevice or pitting corrosion in quiet or low velocity seawater. For it matters not to tubing (or other articles) by which form of corrosion (crevice, pitting, impingement, etc.), it is perforated.

It has now been discovered that the capability of wrought, non age-hardenable cupronickels of the 70/30, /25, /20 and /15 types to resist high velocity seawater, e.g., above 10 feet per second and up to as high as 50 feet per second or possibly higher, can be appreciably enhanced through the incorporation of a small but effective amount of chromium particularly in combination with controlled amounts of iron. Moreover, it has been further found that such alloys do not deleteriously detract from the usual behavior of conventional cupronickels in quiet and low velocity seawater in respect of localized crevice and pitting attack.

It is an object of the present invention to improve the corrosion resistance of wrought cupronickels in seawater.

Another object is to particularly provide copper-nickel alloys capable of delivering a greater degree of resistance than conventional cupronickels to high velocity seawater.

Other objects and advantages will become apparent from the following description taken in conjunction with :FIG. 1 in which there is depicted a graphical correlation between nickel and iron contents in relation to parting corrosion as herein discussed.

Generally speaking, the present invention contemplates providing novel wrought, non age-hardenable articles of manufacture, including condenser and heat exchange tubing, evaporator tubes, pump components, valves, propellers including propeller shafts, shaft sleeves, water boxes, etc., fabricated from copper-nickel alloys containing from not less than 13% to about 37% nickel, from about 3 0.15%, and most beneficially from 0.25% or 0.3%, to not more than about 1.25% chromium, up to 1.5% iron, up to 3% manganese, and the balance essentially copper.

In referring to copper as constituting the balance or essentially the balance of the alloys it is to be understood that other constituents can be present, including incidental elements, e.g., deoxidizing elements and impurities ordinarily associated therewith in small amounts which do not adversely affect the basic characteristics of the alloys. Sulfur, oxygen, nitrogen, hydrogen should be kept to levels consistent with good commercial processing practice. Auxiliary elements can. be present such as up to 0.12%, e.g., up to 0.03%, carbon; up to 0.3%, e.g., up to 0.1% titanium; up to 0.3%, e.g., up to 0.1%, aluminum; up to 0.3%, e.g., up to 0.1%, silicon; up to less than 0.5%, e.g., up to less than 0.15%, zirconium; up to 0.5 e.g., up to 0.1%, columbium; up to 0.15%, e.g., up to 0.05%, beryllium; up to 3%, e.g., up to 0.5%, cobalt; up to less than 0.1%, e.g., less than 0.05%, cerium, and up to less than 0.1%, e.g., less than 0.05%, magnesium.

:In carrying the invention into practice, the nickel should not fall below 13%, and advantageously is at least 15%; otherwise, impingement erosion suffers. On the other hand, exceeding a level of 37% is not warranted in terms of additional cost versus the magnitude of what might be derived by way of other benefits. While alloys in accordance herewith are useful in corrosive environments other than salt water, seawater and the like, in the case of the latter when the nickel content is from 13% to, say, about 25% or 28% a small but elfcctive percentage of iron should be present since it has been determined that the alloys otherwise tend to undesirably exhibit the phenomenon known as parting corrosion, sometimes referred to as selective or preferential corrosion. Usually, this takes the form of a porous copper mass on the surface and is generally observable to the naked eye. It is decidedly beneficial, therefore, for seawater corrosion (and for brackish and polluted waters as well) that the percentages of nickel and iron be correlated as to be represented by a point within the shaded area of FIG. 1.

However, at nickel levels of about 28% or more, "parting corrosion is not of particular concern using conventional heat treatments. But iron, the constituent which efiectively counteracts this phenomenon has been found to reverse its beneficial role by contributing to localized attack (crevice and pitting) in quiet and low velocity, say, below about f.p.s., when present to the excess. Accordingly, in seeking optimum results in inhibiting seawater attack, iron should not exceed 0.65% and preferably is below 0.6%, e.g., 0.5%, when the nickel is approximately 28% and above. In environments of high velocity only, i.e., above 10 or f.p.s., the iron content can be extended above 1% and up to 1.5 at such nickel levels.

Chromium is the constituent responsible for the en hanced resistance to high velocity impingement erosion. With percentages much below 0.15%, this elfectiveness is impaired. If high velocity conditions (up to 50 f.p.s.) were all that would be envisaged in a given application, the chromium level can be as high as 1.25%; however, it has been found that such percentages display a marked propensity to promote crevice and pitting attack in stagnant, quiet and slowly moving seawater. Thus, the chromium should not exceed about 1% for overall crevice, pitting and impingement resistance, and a range of from 0.3% to 0.7% or 0.75% has been determined as ofiering particularly outstanding characteristics since even as the 1% chromium level is approached the capability to reduce impingement erosion is lessened.

With regard to other constituents, it is virtually impossible to avoid the presence of carbon (it is introduced through scrap, crucibles, carbon stirring rods, fuels, etc.), and though it can be present up to 0.12% it, nonetheless, should be held to 0.04% or less, a range of 0.001% to 0.03% being quite satisfactory. A small amount of titanium, 0.05% to 0.25%, and/ or aluminum, 0.05% to 0.25 is quite useful for deoxidation purposes and in contributing to good hot working characteristics. Elements such as vanadium can be tolerated but can deleteriously affect corrosion resistance and is not recommended, apart from being not essential.

While the alloys can be prepared and treated using conventional techniques, it is much preferred, as will be demonstrated herein, that annealing treatments be conducted at temperatures well below 1850" F., a temperature range of 1100 F. to 1650 F., particularly from 1200 F. to about 1500 F. being especially satisfactory.

In order to give those skilled in the art a better ap preciation of the invention, the following illustrative data are given.

A series of alloys were prepared generally using materials of high purity including the electrolytic forms of copper, nickel and chromium. The copper and nickel were first melted down and the chromium thereafter added followed by deoxidants, etc. ingots formed, were hot worked and subsequently cold rolled to strip. Intermediate anneals were used as is customary, the final annealing treatment being between about 1200 F. to 1350 F. which was followed by air cooling. Using the well-known BNFMRA test, specimens (duplicate for the most part) were exposed for 56 days to seawater attack at a velocity of 25 f.p.s. at the world famous marine corrosion laboratory in North Carolina. Compositions both within (identified by numerals) and without (designated by letters) the. invention were tested and are reported together with the impingement erosion results in Table I. The panel specimens were 3 /2" x /2" x 14;" and the seawater temperature was about 23-26 C., except in a few instances in which it was approximately l416 C.

TABLE I Max- Percent W 1 impt. oss, de th Alloy Ni Cr Fe Mn Cu lug/0111. iinl /30 Cupronlckel A 30.7 N.a. 0.01 0.45 an... 1g g N.a. 0.48 0.54 130.1... N.a. N.a. N.a. Bal--- 03.4 18 N.a. 0.69 Na. Bal--. 10.9 20 N.a. 0.05 N01. Bal.-- 22.5 9

0.15 0.05 0.51 Bel-.-

0.27 0.00 0.52 Bel--- 0.27 0.10 0.52 B21.--{ 0.32 0.20 0.55 Bal g-g 0.32 0.48 0.53 Bal-.- 2'? i 0.57 0.05 Bel--- 1 7 "30.5 0.50 0.10 0.53 Bal 1 33.0 0.75 0.10 Bal--. 0.2 1 0 30.7 0.55 0.05 0.40 Bal-.- 5-: i 10- -a0.5 0.75 0.05 0.27 Bel..- 4.4 1 1 11 30.9 v 0.39 0.01 0.17 Bel--. 2.s{ 1 1-2 12 .-a1.2 0.24 0.77 0.1 B21... 41 1 1 12.2 2-5 is 30.4 1.15 0.05 0.40 Bal--- 12.3 1 2 /26 and /20 Cupronickel 1.35 0.15 Na. Bel-.- 41.3 1 1.35 0.20 N.a. Bel.-- 41.2 12 2.10 0.24 N.a. Bel--. 47.2 0 Ne. 0.001 Nil Be]... 40.2 10 0.35 0.05 0.40 B211... 5:; 1 N51. 0.05 0.07 Bal..- 33:3 Na. 1.2 0.10 Bal.-. 3% i 15 22.2 0.40 01 0 2s Bal 1 See footnotes at end of table.

TABLE IContinued l Alloy D contained 0.55% vanadium. 1 Alloy E contained 0.56% vanadium.

NOTE.A11oys A and B were commercially produced. Alloys and 8 were vacuum melted, air melting being otherwise used.

Again, it will be noted that the results of the alloys (Alloys 10, 11 and 22-24) containing chromium were significantly superior to the chromium-free alloys.

As indicated above, whatever improvement is attained in minimizing high velocity impingement corrosion in sea water and the like it would be to little avail for a vast number of commercial applications if localized corrosion was detrimentally affected in quiet or low velocity seawater. In this regard, specimens were also subjected to tests in both quiet seawater and seawater flowing at a rate of 2. f.p.s., the results of which are set forth in Table III. In this instance, the corrosion rate in mils per year (m.p.y.) as well as crevice corrosion data, taken at the location at which the specimens were secured in their holders, the holders, in effect, forming a crevice and also pitting elsewhere on the panel specimens were determined. Tests were conducted for a period of 6 months in all instances.

TABLE III Seawater corrosion behavior Quiet 2 feet /s eccd Percent Rate Else- Rate Else- Alloy Ti Cr Fe Mn (m.p.y.) Crev. where (m.p.y.) Crev. where 70/30 Cupronickel 75/25 and 80/20 Cupronickel 11 85/15 Cupronlekel From a perusal of the data set forth in Table I it will It will be observed the data reflect that the chromiumbe noted that amounts of chromium contemplated herecontaining alloys within the invention compared quite with consistently improved impingement erosion over the favorably to cupronickels of the conventional type. It full range of alloys tested. 60 is Worthy of mention to point out that Alloys 10 and 12 While the data in Table I concern a jet test conducted relatively high in iron content did exhibit a susceptibilat 25 f.p.s., representative results are given in Table II ity to attack. As indicated previously herein, for alloys in which the BNFMRA tests were conducted at '10 and containing above about nickel the iron content f.p.s., respectively for a 70/30 cupronickel. should not exceed 0.6% or 0.65% in applications where the alloys will be exposed to quiescent or low velocity TABLE II seawater use.

weightless, Maxim The purpose of the data set forth in Table IV is to Percent mg. 0111. depth, mils aflFord an indication of what might be expected in terms Alloy Ni Cr Fe Mn 101. 13. 15 fps. 10 1. 1.5. 15 i.p.s. 0f P Corrosion in both quiet and low Velocity N 31 12 seawater (2 f.p.s.) when the proper correlation between 3 nickel and iron is not observed. While the test is based upon visual inspection, it is nonetheless considered that 8 alloys in which a moderate amount of parting corrosion occurred would be unsuitable for long term seawater systems. However, by maintaining the nickel-iron relation such that it is represented by a point within the shaded area of FIG. 1, this adverse effect is greatly minimized.

and brackish, polluted and fresh waters. In addition to marine environments, including marine atmospheres,

As has been previously indicated above herein, final annealing treatments of 1850 F. and upwards are considerably less advantageous than those conducted at lower temperatures, e.g., 1250 F.-l350 F. This is illustrated by the data in Table V, the data generally indicating a superior resistance to impingement erosion with the lower temperatures. In this connection, the grain size of the alloys in accordance herewith should preferably not exceed about 0.05 millimeter.

oceanography, desalination equipment, the instant alloys and components fabricated therefrom can be gainfully used in ammoniacal and sulfur bearing environments:

Although the present invention has been described in conjunction with preferred embodiments, it is to be understood that modifications and variations can 'be resorted to without departing from the spirit and scope of the invention as those skilled in the art will readily understand. Such modifications and variations are considered tobe TABLE V Corrosion Percent rate (m.p.y.) Maximum implngment Cr Fe Mn Heat treatment Quiet 2 i.p.s. depth, mils 0. 27 0. 06 0. 52 1,250 F./A.C..-- 4 0. 8 1 0. 27 0. 06 0. 52 1,850 F./W.Q, 0. 9 1. 4 3 0'- 27 0. 16 0- 52 1, 250 F./A.C 0- 3 0- 4 1 O. 27 O. 16 0. 52 1,850 F./W.Q,- 0. 4 O- 4 1. 5 0. 32 0. 29 0. 55 1,250 F./A.C- 0. 3 0. 2 l 0. 32 0. 29 0- 55 1,550 F./W.Q 0. 8 1. 8 6 0. 32 0. 48 0. 58 l,250 F./A.C 0. 3 0. 7 1 0. 32 0. 4B 0. 58 1,850 F./W.Q 0. 3 l. 1 3 0. 50 0. 16 0. 53 1,250 F./.A.O 0. 3 0- 6 l 0. 50 0. l6 0. 53 1,950 F.IW.Q- l. 2 1. 2 3 0. 52 0. 05 0. l,950 F./W.%. 0. 9 2. 0 6 0. 52 0. 05 0. 40 1,950 F./W. 0. 9 2. 0 5 0. 54 0. 47 0. 48 1,250 F. A.C- 0. 3 0. 7 1 0. 54 0. 47 0. 48 1,950 F.[W.Q, 0. 4 3. 3 3 0. 55 0. 29 0. 50 l,250 F./A.C. 0. 4 0. 5 1 0- 55 0. 29 0. 50 l,950 F. .Q- 0. 6 1. 1 4

NorE.-A.C.=Air cooled. W.Q.=Water quenched.

Since the subject alloys are primarily intended for seawater and salt water applications and also brackish, polluted and fresh water, especially for tubing and piping, a particular attribute of the alloys is that impingement erosion attack being reduced thinner wall sections can be utilized than otherwise might be the case. This is a decided economic advantage.

In addition to the alloys above described the following are particularly advantageous: from 14% to 17% nickel, up to 0.6% or 0.5 iron the nickel and iron being related to fall within the shaded area of FIG. 1, from 0.25% to 0.75% chromium, up to 1% or 2% manganese, the balance essentially copper. The same chromium, manganese and iron percentages afford outstanding results with nickel ranges of 18% to 22%, 23% to 27% and from 28% to 33%. In elfect, such constituents and ranges run the full nickel complement of 15% to 37%. It should be added that the chromium content should be elfective chromium, i.e., chromium in virtually uncombined form; otherwise, its effectiveness can be impaired. For this reason, carbon should preferably be held to not more than 0.03%.

In addition condenser and heat exchanger tubing, pip ing and other articles mentioned before herein, other fabricated products can be manufactured from the alloys in accordance herewith, including flanges, wrought valves, valve stems, exhaust lines, capillary tubing, oil coolers, shaped tubing for desalination processes, screens and filters for seawater, wire for moorings, etc. Such articles can be and are collectively referred to as wrought, fabricated, structural components. The term seawater for purposes herein and in the claims is intended to include salt water within the purview and scope of the invention and appended claims.

We claim:

1. As a new article of manufacture, a wrought, fabricated structural component formed from a corrosion resistant copper-nickel alloy consisting of more than 15% and up to 25 nickel, iron present in an amount up to 1.5% with the proviso that the nickel and iron are correlated so as to represent a point within the shaded area of the accompanying drawing whereby resistance to parting corrosion is enhanced, a small 'but eifective amount of chromium sufiicient to improve the resistance of the component to high velocity seawater impingement erosion, the chromium content being not greater than about 0.75%, up to 3% manganese, up to 0.12% carbon, up to 0.3% titanium, up to 0.3% aluminum, up to 0.3% silicon, up to 0.5% columbium, up to 0.15% beryllium, up to 3% cobalt, up to 0.1% cerium, up to 0.5% zirconium, up to 1% magnesium, and the balance essentially copper.

2. A component in accordance with claim 1 in which the chromium content is about 0.25% to about 0.75%.

3. A component in accordance with claim 1 in which the nickel is about 18% to about 22%.

4. A copper-nickel alloy characterized by improved resistance to high velocity seawater impingement erosion and consisting of more than 15% and up to about 25% nickel, iron present in an amount up to 1.5%, with the proviso that the nickel and iron are correlated so as to represent a point within the shaded area of the accompanying drawing whereby reistance to parting corrosion is enhanced, a small but effective amount of chromium s tfliQieut to improve the resistance of the alloy to high velocity seawater impingement erosion, the chromium content being not greater than about 0.75%, up to 3% manganese, up to 0.12% carbon, up to 0.3% titanium, up to 0.4% aluminum, up to 0.3% silicon, up to 0.5% columbium, up to 0.15% beryllium, up to 3% cobalt, up to 0.1% cerium, up to 0.5 zirconium, up to 1% magnesium, and the balance essentially copper.

5. An alloy in accordance with claim 4 in which the chromium is about 0.25% to about 0.75%.

6. An alloy in accordance with claim 5 containing about 18% to about 22% nickel.

7. An alloy in accordance with claim 4 in which the carbon content does not exceed 0.03%.

References Cited UNITED STATES PATENTS 2,074,604 3/1937 Bolton 75-159 3,488,188 1/1970 Paces et a1. 75-159 1,557,025 1925 Cochrane 75-159 2,067,306 1/1937 Wilkins 75-159 10 2,067,308 1/ 1937 Wilkiiis 75-159 2,430,306 11/ 1947 Smith 75-159 3,053,511 9/1962 Godfrey 75-159 FOREIGN PATENTS 61,686 11/ 1945 Netherlands 75-159 473,750 5/ 1951 Canada 75-159 338,676 11/ 1930 Great Britain 75-159 OTHER REFERENCES Badia et 31.: Trans. of ASM, vol. 60, 1967, pp. 395- s.

Hibbard et al.: Trans. of AIME, vol. 175, 1948, pp. 283- 295.

CHARLES N. LOVELL, Primary Examiner US. Cl. X.R.

22 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent: No. 3,738,106 D t d April 17, 1973 Inventor) Frank Arthur Badia, David Barber Anderson & Gary Neil Kirby I It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 5, Table Continued, for "Alloy 19. 15.6 0-44 0-38 0-48" 5....1 "Alloy 19 ..15.5 0.44 0.47' 0.48";

Column 5, Table II, for "Weight loss, mg .cm read "Weight loss, mg ./cm

Column 6, line 13 insert parenthesis before "taken";

line 15 insert parenthesis after "crevice";

Table III, second column, for "Ti" read "Ni";

7 Section "75/25 and 80/ 20 Cupronickel" delete "11" last column;

Table v, Alloy 28, line 1,

for "30.7 0.52 0.05 0.40 1,950F./W.Q. 0.9 2.0'5"

read"30.7 0.52 0.05 0.40 l,250F./A.C. 0.3 0.4 l"

Signed and sealed this 22nd day of January 197M.

(SEAL) Attest:

EDWAED M.ELET0EER,JR. RENE D. TEGTMEYER Attesting Officer Acting Commissioner of Patents 

